在不改变原始数据框的情况下创建数据框副本

Question

我试图创建一个函数，可以在不更改原始数据框的情况下更改数据框副本的值。这是我到目前为止有：

def home_undervalued(df): 
    local_df = df 
    local_df['total_games'] = 0 
    local_df['total_wins'] = 0 
    cond_1 = local_df['predicted_spread'] > local_df['vegas_spread'] 
    cond_2 = local_df['actual_spread'] > local_df['vegas_spread'] 
    cond_3 = local_df['predicted_spread'] - local_df['vegas_spread'] >= 3 

    local_df.loc[cond_1 & cond_3 , 'total_games'] = 1 
    local_df.loc[cond_1 & cond_2 & cond_3 , 'total_wins'] = 1 

    total_games = sum(local_df.total_games) 
    total_wins = sum(local_df.total_wins) 

    return float(total_wins)/float(total_games) 

我然后调用函数

home_undervalued(df) 

看来工作，但后来我意识到了DF值[“total_games”]和df [” total_wins']已经改变。我试图改变local_df的值，但保留值df。有想法该怎么解决这个吗？

Answer 1

local_df = df只是创建了一个参考df名为local_df。如果你想创建一个完整的其他数据框（顺便说一下，我不建议），你可以创建一个新的数据框，如df.copy(deep=True)

Answer 2

只需使用的DataFrame

local_df = df.copy(deep=True) 

copy方法在这一行以后在local_df将存储的df副本。